MC908MR16CFUE Datasheet, PDF (214/282 Pages) Freescale Semiconductor, Inc – On-chip programming firmware for use with host personal computer, Clock generator module (CGM)

Serial Peripheral Interface Module (SPI)
Table 15-4. SPI Master Baud Rate Selection
SPR1:SPR0
00
01
10
11
Baud Rate Divisor (BD)
2
8
32
128
Use this formula to calculate the SPI baud rate:
Baud rate = ^{C-----G----M------O----U-----T--}
2 × BD
where:
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
15.12.3 SPI Data Register
The SPI data register consists of the read-only receive data register and the write-only transmit data
register. Writing to the SPI data register writes data into the transmit data register. Reading the SPI data
register reads data from the receive data register. The transmit data and receive data registers are
separate registers that can contain different values. See Figure 15-2.
Address: $0046
Bit 7
6
Read: R7
R6
Write: T7
T6
Reset:
5
4
3
2
R5
R4
R3
R2
T5
T4
T3
T2
Indeterminate after reset
1
Bit 0
R1
R0
T1
T0
Figure 15-16. SPI Data Register (SPDR)
R7:R0/T7:T0 — Receive/Transmit Data Bits
NOTE
Do not use read-modify-write instructions on the SPI data register since the
register read is not the same as the register written.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
214
Freescale Semiconductor